The City of London is widely referred to simply as the City (differentiated from the phrase "the city of London" by capitalising City) and is also colloquially known as the Square Mile, as it is 1.12 sq mi (720 acres)[4] in area. Both of these terms are also often used as
metonyms for the United Kingdom's trading and
financial services industries, which continue a notable history of being largely based in the City.[5] The
name London is now ordinarily used for a far wider area than just the City. London most often denotes the sprawling London metropolis, or the 32 London boroughs, in addition to the City of London itself. This wider usage of London is documented as far back as 1888, when the County of London was created.[6]

The City is a major business and
financial centre.[7] Throughout the 19th century, the City was the world's primary business centre, and it continues to be a major meeting point for businesses.[8] London came top in the
Worldwide Centres of Commerce Index, published in 2008. The insurance industry is focused around the eastern side of the City, around
Lloyd's building. A secondary financial district exists outside of the City, at
Canary Wharf, 2.5 miles (4 km) to the east.

The City has a resident population of 9,401 (
ONS estimate, mid-2016) but over 300,000 people commute to and work there. About three quarters of the jobs in the City of London are in the financial, professional, and associated business services sectors.[9] The legal profession forms a major component of the northern and western sides of the City, especially in the
Temple and
Chancery Lane areas where the
Inns of Court are located, of which two—
Inner Temple and
Middle Temple—fall within the City of London boundary.

Origins

It used to be widely held that Londinium was first established by merchants as a trading port on the tidal
Thames in around 47 AD, during the early years of the
Roman occupation of Britain. However, this date is only supposition. The Romans have left no record of when or how the city was founded and the first time they mention the city is in the annals of
Tacitus (in 61 AD) when he relates how Londinium was among a group of important cities sacked by the
Iceni, led by their queen,
Boudica.

Many historians now believe London was founded some time before the
Roman conquest of Britain in 43 AD. They base this notion on evidence provided by both archaeology and Welsh literary legend. Archaeologists have claimed that as much as half of the best
British Iron Age art and metalwork discovered in Britain has been found in the London area.[10] One of the most prominent examples is the famously horned "
Waterloo Helmet" dredged from the Thames in the early 1860s and now exhibited at the
British Museum.[11]

Also, according to an ancient Welsh legend, a king named
Lud son of Heli substantially enlarged and improved a pre-existing settlement at London which afterwards came to be renamed after him. The same tradition relates how this Lud son of Heli was later buried at
Ludgate (Welsh: Porthlud).[12]

Llydd was the eldest son. And after his father (
Beli Mawr) was dead he took the government of the island. And he strengthened the walls of Llvndain, surrounded the city with many
farmsteads, and lived in it the greater part of the year. And he had built within the city walls splendid buildings the like of which were not seen in all countries. And he called it Kaer Lvdd; and in the end it was called Kaer Lvndain. And, after the coming of the alien nation into it, it was called Kaer Lwndwn.[13]

—Ystorya Brenhined y Brytanyeit, Jesus MS. LXI.

Nevertheless, after the conquest the Romans certainly developed the settlement and port, with its centre roughly where the shallow stream the
Walbrook met the Thames. After the city had been destroyed by Boudica in 60 AD it was entirely rebuilt as a planned settlement (a civitas), and the new walled town was prosperous and grew to become the largest settlement in
Roman Britain by the end of the 1st century. By the beginning of the 2nd century, Londinium had replaced
Camulodunum (Colchester) as the capital of Roman Britain ("Britannia").

At its height, the Roman city had a population of approximately 45,000–60,000 inhabitants. Londinium was an ethnically diverse city, with inhabitants from across the Roman Empire, including natives of Britannia,
continental Europe, the
Middle East, and
North Africa.[14] The Romans built the
London Wall some time between 190 and 225 AD. The boundaries of the Roman city were similar to those of the City of London today, though Londinium did not extend further west than
Ludgate or the
Fleet, and the mid-estuary Thames was undredged and wider than it is today thus, the City's shoreline was north of its present position. The Romans built a bridge across the river, as early as 50 AD, near to today's
London Bridge.

A number of Roman sites and artefacts can be seen in the City, including the
Temple of Mithras, sections of the London Wall (at the
Barbican and near Tower Hill), the
London Stone and remains of the amphitheatre beneath the
Guildhall. The
Museum of London holds many of the Roman finds, has permanent Roman exhibitions and holds research collections.

Decline

By the time the London Wall was constructed, the City's fortunes were in decline, and it faced problems of plague and fire. The Roman Empire entered a long period of
instability and decline, including the
Carausian Revolt in Britain. In the 3rd and 4th centuries, the city was under attack from
Picts, Scots, and
Saxon raiders. The decline continued, both for Londinium and the Empire, and in 410 AD the Romans withdrew entirely from Britain. Many of the Roman public buildings in Londinium by this time had fallen into decay and disuse, and gradually after the formal withdrawal the city became almost (if not, at times, entirely) uninhabited. The centre of trade and population moved away from the walled Londinium to
Lundenwic ("London market"), a settlement to the west, roughly in the modern day
Strand/
Aldwych/
Covent Garden area.[citation needed]

Anglo-Saxon restoration

During the Anglo-Saxon
Heptarchy, the London area came in turn under the Kingdoms of
Essex,
Mercia, and later
Wessex, though from the mid 8th century it was frequently under the control or threat of the
Vikings.

Bede records that in 604 AD
St Augustine consecrated
Mellitus as the first bishop to the
Anglo-Saxon kingdom of the
East Saxons and their king,
Sæberht. Sæberht's uncle and overlord,
Æthelberht, king of
Kent, built a church dedicated to St Paul in London, as the seat of the new bishop.[15] It is assumed, although unproven, that this first Anglo-Saxon cathedral stood on the same site as the later medieval and the present cathedrals.[citation needed]

Alfred the Great,
King of Wessex and arguably the first king of the "English", occupied and began the resettlement of the old
Roman walled area, in 886, and appointed his son-in-law
Earl Æthelred of Mercia over it as part of their reconquest of the Viking occupied parts of England. The refortified Anglo-Saxon settlement was known as
Lundenburh ("London Fort", a
borough). The historian Asser said that "Alfred, king of the Anglo-Saxons, restored the city of London splendidly ... and made it habitable once more."[16] Alfred's "restoration" entailed reoccupying and refurbishing the nearly deserted Roman walled city, building quays along the Thames, and laying a new city street plan.[17]

Alfred's taking of London and the rebuilding of the old Roman city was a turning point in history, not only as the permanent establishment of the City of London, but also as part of a unifying moment in early England, with Wessex becoming the dominant English kingdom and the repelling (to some degree) of the Viking occupation and raids. While London, and indeed England, were afterwards subjected to further periods of Viking and Danish raids and occupation, the establishment of the City of London and the
Kingdom of England prevailed.[18]

In the 10th century,
Athelstan permitted eight
mints to be established, compared with six in his capital,
Winchester, indicating the wealth of the city.
London Bridge, which had fallen into ruin following the Roman evacuation and abandonment of Londinium, was rebuilt by the Saxons, but was periodically destroyed by Viking raids and storms.

As the focus of trade and population was moved back to within the old Roman walls, the older Saxon settlement of Lundenwic was largely abandoned and gained the name of Ealdwic (the "old settlement"). The name survives today as
Aldwych (the "old market-place"), a name of a street and an area of the
City of Westminster between
Westminster and the City of London.

About 1130,
Henry I granted a
sheriff to the people of London, along with control of the county of
Middlesex: this meant that the two entities were regarded as one administratively (not that the county was a dependency of the City) until the
Local Government Act 1888.[19] By 1141 the whole body of the citizenry was considered to constitute a single community. This 'commune' was the origin of the
City of London Corporation and the citizens gained the right to appoint, with the king's consent, a Mayor in 1189—and to directly elect the Mayor from 1215.

From medieval times, the City has been composed of
25 ancient wards, each headed by an
Alderman, who chairs
Wardmotes, which still take place at least annually. A
Folkmoot, for the whole of the City held at the outdoor cross of
St Paul's Cathedral, was formerly also held. Many of the medieval offices and traditions continue to the present day, demonstrating the unique nature of the City and its
Corporation.

In 1381, the
Peasants' Revolt affected London. The rebels took the City and the Tower of London, but the rebellion ended after its leader, Wat Tyler, was killed during a confrontation that included Lord Mayor
William Walworth.

The 1666 Great Fire as depicted in a 17th-century painting: it depicts Old London Bridge, churches, houses, and the Tower of London as seen from a boat near Tower Wharf

The City was burned severely on a number of occasions, the worst being in 1123 and (more famously) in the
Great Fire of London in 1666. Both of these fires were referred to as the Great Fire. After the fire of 1666, a number of plans were drawn up to remodel the City and its street pattern into a
renaissance-style city with planned urban blocks, squares and boulevards. These plans were almost entirely not taken up, and the medieval street pattern re-emerged almost intact.

Early modern period

By the late 16th century, London increasingly became a major centre for banking, international trade and commerce. The
Royal Exchange was founded in 1565 by Sir
Thomas Gresham as a centre of commerce for London's merchants, and gained Royal patronage in 1571. Although no longer used for its original purpose, its location at the corner of
Cornhill and
Threadneedle Street continues to be the geographical centre of the City's core of banking and financial services, with the
Bank of England moving to its present site in 1734, opposite the Royal Exchange on Threadneedle Street. Immediately to the south of Cornhill,
Lombard Street was the location from 1691 of
Lloyd's Coffee House, which became the world-leading insurance market. London's insurance sector continues to be based in the area, particularly in
Lime Street.

In 1708,
Christopher Wren's masterpiece,
St Paul's Cathedral, was completed on his birthday. The first service had been held on 2 December 1697, more than 10 years earlier. It replaced the original St Paul's, which had been completely destroyed in the Great Fire of London, and is considered to be one of the finest cathedrals in Britain and a fine example of
Baroque architecture.

Growth of London

The 18th century was a period of rapid growth for London, reflecting an increasing national population, the early stirrings of the
Industrial Revolution, and London's role at the centre of the evolving
British Empire. The urban area expanded beyond the borders of the City of London, most notably during this period towards the
West End and
Westminster.

Expansion continued and became more rapid by the beginning of the 19th century, with London growing in all directions. To the
East the
Port of London grew rapidly during the century, with the construction of many docks, needed as the Thames at the City could not cope with the volume of trade. The arrival of the railways and the
Tube meant that London could expand over a much greater area. By the mid-19th century, with London still rapidly expanding in population and area, the City had already become only a small part of the wider metropolis.

The City's population fell rapidly in the 19th century and through most of the 20th century, as people moved outwards in all directions to London's vast
suburbs, and many residential buildings were demolished to make way for office blocks. Like many areas of London and other British cities, the City fell victim to large scale and highly destructive aerial bombing during
World War II, especially in
the Blitz. Whilst St Paul's Cathedral survived the onslaught, large swathes of the area did not and the particularly heavy raids of late December 1940 led to a
firestorm called the
Second Great Fire of London.

There was a major rebuilding programme in the decades following the war, in some parts (such as at the Barbican) dramatically altering the urban landscape. But the destruction of the older historic fabric allowed the construction of modern and larger-scale developments, whereas in those parts not so badly affected by bomb damage the City retains its older character of smaller buildings. The street pattern, which is still largely medieval, was altered slightly in places, although there is a more recent trend of reversing some of the post-war modernist changes made, such as at
Paternoster Square.

The main residential section of the City today is the
Barbican Estate, constructed between 1965 and 1976. The
Museum of London is based there, as are a number of other services provided by the Corporation.